$$\left({\frac{{\mathtt{9}}}{{\mathtt{12}}}}\right){\mathtt{\,\times\,}}\left({\frac{{\mathtt{9}}}{{\mathtt{12}}}}\right) = {\frac{\left({\mathtt{9}}{\mathtt{\,\times\,}}{\mathtt{9}}\right)}{\left({\mathtt{12}}{\mathtt{\,\times\,}}{\mathtt{12}}\right)}}$$ nun kannst du kürzen
$$\left({\frac{{\mathtt{9}}}{{\mathtt{12}}}}\right){\mathtt{\,\times\,}}\left({\frac{{\mathtt{9}}}{{\mathtt{12}}}}\right) = {\frac{\left({\mathtt{9}}{\mathtt{\,\times\,}}{\mathtt{9}}\right)}{\left({\mathtt{12}}{\mathtt{\,\times\,}}{\mathtt{12}}\right)}}$$ nun kannst du kürzen